If you are buying at
Halfords with their 20% off all accessories offer, then I would suggest buying the Topeak Super Tourist DX rack as it is one of the best you can get. Don't bother with that other one you posted the Axiom whatever rubbish.
As Fossy recommends get Ortlieb Roller Classic panniers - totally waterproof and 5 years warranty, or my preference is for Vaude Aqua which are similar, again totally WP, but a shade more robust than the Ortlieb panniers, if that is possible, but this is just me being picky. They have a 3 year warranty. I would go for the larger rear panniers as you don't have to fill them and you can use only one if you want and still have plenty of space to carry warm layers when you are riding in winter or wet weather gear. This is what I do.
Altura are ok but not as good as Ortlieb or Vaude panniers.
HTH.